Webobject problem: [java.lang.NullPointerException] null:<WOApplication>: Cannot be i

Hello!
I'm new in developing WebObjects and at the beginning, I was using a Mac on which everything was already installed (eclipse, wolips, webobjects...). Now I want to develope the new features for the software on my Mac Book Pro. So I installed the required tools, but I can't get the source code (of the software I'm developing) to run.
The weird thing is, that on the old computer, the same source code runs without any problem, but on my mac book pro, I got a weird Error:

[2009-6-29 9:10:15 CEST] <main> <WOApplication>: Cannot be initialized.null
[2009-6-29 9:10:15 CEST] <main> A fatal exception occurred: <WOApplication>: Cannot be initialized.
[2009-6-29 9:10:15 CEST] <main> com.webobjects.foundation.NSForwardException [java.lang.NullPointerException] null:<WOApplication>: Cannot be initialized.
at com.webobjects.appserver.WOApplication.<init>(WOApplication.java:918)
at feedback.Application.<init>(Application.java:38)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at java.lang.Class.newInstance0(Class.java:350)
at java.lang.Class.newInstance(Class.java:303)
at com.webobjects.appserver.WOApplication.main(WOApplication.java:547)
at feedback.Application.main(Application.java:105)
Caused by: java.lang.NullPointerException
at com.webobjects.appserver.WOApplication._initializeRapidTurnaroundMode(WOApplication.java:923)
at com.webobjects.appserver.WOApplication.<init>(WOApplication.java:846)
... 9 more

Can it be, that the newest version of WO is not the "same" anymore...? I mean this error happens in a standard class of WebObject....?!
When I'm creating a new Webobject project (for example the Hello World), the code runs without any errors, so webobject must be installed correctly....

I hope anyone can help me to fix this problem, because I tried to fix this for already many days :-(!
Thx
Greets

Is it possible, that if you are using the newest WO instead of a very older WO, then you have to "convert" your project?

Hmm... no idea?
I found out, that it could be that some systempaths has changed in Leopard (compared with Tiger) OR Xcode v.3 and Xcode v.2 are different...